Designs for the control room in a nuclear plant continue to evolve based on operating experience. In particular, studies since the Three-Mile Island accident in March of 1979 have not only pointed out weaknesses in plant system designs, plant development procedures, training, maintenance and testing programs but an underestimation of the potentially critical role of operator stress during emergencies. Increasingly, the emphasis on new reactor designs centers on "passive" reactor operations, a term meaning that the plant operations are in a sense so inherently stable that they will self regulate in the absence of human control, at least for the probable time that the emergency lasts.
Seen in terms of passive operations, the evolution of nuclear reactor design techniques since the Three-Mile Island incident stress a "holistic" approach in designing a control room that minimizes operator stress. Designing portions of the control room in relative isolation to other parts of the system room is no longer considered. Rather, control room designs now should take into account the operator requirements during emergency conditions by providing a layout that is capable of sustaining personnel and equipment when power failures or reductions take place. When there is a nuclear plant operating problem, key personnel must remain on site as long as possible, in the control room. During that time, however, the normal heating and ventilating system HVAC may cease. The temperature in the control room will gradually rise from heat generated by the equipment in the control room. Even so, key personnel must remain in the control room, relatively free of the distraction of elevated room temperature.